• 대한수학회지
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• 제38권3호
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• pp.595-611
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• 2001

Let Q(n,1) be the set of even unimodular positive definite integral quadratic forms in n-variables. Then n is divisible by 8. For A[X] in Q(n,1), the theta series $\theta$(sub)A(z) = ∑(sub)X∈Z(sup)n e(sup)$\pi$izA[X] (Z∈h (※Equations, See Full-text) the complex upper half plane) is a modular form of weight n/2 for the congruence group Γ$_1$(8) = {$\delta$∈SL$_2$(Z)│$\delta$≡()mod 8} (※Equation, See Full-text). If n$\geq$24 and A[X], B{X} are tow quadratic forms in Q(n,1), the quotient $\theta$(sub)A(z)/$\theta$(sub)B(z) is a modular function for Γ$_1$(8). Since we identify the field of modular functions for Γ$_1$(8) with the function field K(X$_1$(8)) of the modular curve X$_1$(8) = Γ$_1$(8)＼h(sup)* (h(sup)* the extended plane of h) with genus 0, we can express it as a rational function of j(sub) 1,8 over C which is a field generator of K(X$_1$(8)) and defined by j(sub)1,8(z) = $\theta$$_3$(2z)/$\theta$$_3$(4z). Here, $\theta$$_3$ is the classical Jacobi theta series.

• 대한수학회보
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• 제54권3호
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• pp.839-874
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• 2017

Our goal is to establish and prove the almost sure central limit theorems for some order statistics $\{M_n^{(k)}\}$, $k=1,2,{\ldots}$, formed by stochastic processes ($X_1,X_2,{\ldots},X_n$), $n{\in}N$, the distributions of which are defined by certain Archimedean copulas. Some properties of generators of such the copulas are intensively used in our proofs. The first class of theorems stated and proved in the paper concerns sequences of ordinary maxima $\{M_n\}$, the second class of the presented results and proofs applies for sequences of the second largest maxima $\{M_n^{(2)}\}$ and the third (and the last) part of our investigations is devoted to the proofs of the almost sure central limit theorems for the k-th largest maxima $\{M_n^{(k)}\}$ in general. The assumptions imposed in the first two of the mentioned groups of claims significantly differ from the conditions used in the last - the most general - case.

• Korean Journal of Mathematics
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• 제22권1호
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• pp.29-36
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• 2014

The limiting diffusion of special diploid model can be defined as a discrete generator for the rescaled Markov chain. Choi([2]) defined the operator of projection $S_t$ on limiting diffusion and new measure $dQ=S_tdP$. and showed the martingale property on this operator and measure. Let $P_{\rho}$ be the unique solution of the martingale problem for $\mathcal{L}_0$ starting at ${\rho}$ and ${\pi}_1,{\pi}_2,{\cdots},{\pi}_n$ the projection of $E^n$ on $x_1,x_2,{\cdots},x_n$. In this note we define $$dQ_{\rho}=S_tdP_{\rho}$$ and show that $Q_{\rho}$ solves the martingale problem for $\mathcal{L}_{\pi}$ starting at ${\rho}$.

• Journal of Chest Surgery
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• 제9권2호
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• pp.265-270
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• 1976

Implantation of a permanent pacemaker is a widely accepted procedure for the patient with complete heart block.As a result of these device, the prognosis for patients with Adams-Stokes syndrome caused by complete A-V block and other cardiac arrhythmia have become much more optimistic. Permanent pacemaker implantation by means of a transvenous approach has made the operative risk much less and the procedure simpler. However, a number of complications have been reported in the literature regarding transvenous endocardial pacemaker implantation during the last a decade. The patient presented in this paper is a 26-year old girl who was implanted with a permanent pacemaker at 14 years of age because of a congenital A-V block. Following first exchange of pulse generator, the electrode (lead) was fractured, so that by the pulse generator, a change to the transvenous technique of implantation was made, After this, there were episodes of recurrent wound infection on three occasions, even though the site of pulse generator implantation was exchanged to the contralateral side of chest wall, massive doses of antibiotics were administered and sensitivity tests for coagulase positive staphylococcal infection were performed. Though there was no definite evidence of blood stream infection by blood culture, we decided not to use the transvenous technique and not to implant the pulse generator in the chest wall because the venous system and the entire anterior chest wall appeared to be diseased or contaminated by virulent pyogenic organisms. Finally this intractable systemic and local wound infection was successfully controlled by myocardial lead implantation via a subxiphoid approach and implantation of the pulse generator far down in the abdominal wall. The causes and routes of recurrent wound infection and possible blood born infection in this particular patient are still obscure. We strongly believe that myocardial pacemaker implantation is much safer than transvenous endocardial pacemaker implantation & myocardial pacemaker implantation is a definite method for controlling such an intractable wound infection. following transvenous pacemaker implantation.

• 한국전자통신학회논문지
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• 제13권2호
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• pp.383-390
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• 2018

셀룰라 오토마타(이하 CA)는 LFSR보다 난수성이 우수하여 여러 분야에 LFSR의 대안으로 응용되고 있다. 그러나 주어진 다항식에 대응하는 CA를 구성하는 것이 LFSR보다 어렵다. Cattell 등과 Cho 등은 기약다항식들이 CA-다항식임을 보였다. 그리고 Cho 등과 Sabater 등은 기약다항식의 거듭제곱에 대응하는 90/150 CA의 합성 방법을 제시하였다. 이것은 수축생성기에 적용가능하다. Swan은 유한체 GF(2) 상에서 3항 다항식의 기약인수의 개수의 홀짝성을 분석하였다. 이런 3항 다항식들은 유한체 확장을 구현할 때 실제로 중요한 역할을 한다. 본 논문에서는 3항 다항식들 $x^{2^n-1}+X+1$ ($n{\geq}2$)이 CA-다항식임을 보인다. 또한 3항 다항식들 $x^{2^a(2^n-1)}+x^{2^a}+1$ ($n{\geq}2$, $a{\geq}0$)이 CA-다항식임을 보인다.

• Nuclear Engineering and Technology
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• 제31권5호
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• pp.512-521
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• 1999

A feasibility study was performed to design an epithermal neutron beam for BNCT using the neutron of 2.45 MeV on the average produced from $^2H(d,n)^3$He reaction induced by plasma focus in the z-pinch instead of the conventional accelerator-based $^3H(d, n)^4$He neutron generator. Flux and spectrum were analyzed to use these neutrons as the neutron source for BNCT. Neutronic characteristics of several candidate materials in this neutron source were investigated Using MCNP Code, and $^7LiF$ ; 40%Al + 60%$AIF_3$, and Pb Were determined as moderator, filter, and reflector in an epithermal neutron beam design for BNCT, respectively. The skin-skull-brain ellipsoidal phantom, which consists of homogeneous regions of skin-, bone-, or brain-equivalent material, was used in order to assess the dosimetric effect in brain. An epithermal neutron beam design for BNCT was proposed by the repeated work with MCNP runs, and the dosimetric properties (AD, AR, ADDR, and Dose Components) calculated within the phantom showed that the neutron beam designed in this work is effective in tumor therapy. If the neutron source flux is high enough using the z-pinch plasma, BNCT using the neutron source produced from $^2H(d,n)^3$He reaction will be very feasible.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 추계학술대회 논문집
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• pp.423-426
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• 2009

POSTECH Graduate School of Wind Energy is trying to upgrade the PMSG used for Unison U50 to 900 kW class. Intensive optimization efforts are carried out the reduce the axial size and total weight of the generator while increasing the rated output to 900 kW. The generator features 3.32m stator inner radius, 671mm stator length, 84 pole, 25 rated rpm and 31.6kN/$m^2$ shear force density. To reduce the gross weight, the stronger magnetic material is applied with optimal magnet size resulting lowest cogging torque. Also, instead of stator skewing the stator, the magnet position along the circumference is optimized to further reduce the cogging torque. This scheme eliminates the stator skewing procedure and may enhance the productivity. This method also reduces the total harmonic distortion. In this report, upgrade method, no-load line to line voltage and phase voltage, cogging torque, loss calculations and thermal analysis are presented.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.283-289
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• 1997

A 500Wh class high-speed Flywheel Energy Storage System (FESS) driven by a built-in BLDC motor/generator has been designed, which runs from 30000 to 60000rpm nominally. Due to the motor/generator inside, the flywheel rotor made of composites supported by PM/EM hybrid bearing system has a shape of bell or pendulum and thus requires accurate rotordynamic analyses and prediction of its dynamic behavior to secure the operating reliability. Rotordaynamic analyses of the flywheel rotor-bearing system revealed that the bell shaped rotor has two conical rigid-body modes in the system operating range and the first conical mode, of which nodal point lies in the radial EM bearing position, can adversely affect the dynamic response of the rotor at the corresponding critical speed. To eliminate the possibility of wild behavior of the rotor, two guide bearings are adopted at the upper end of the rotor and motor/generator. It was also revealed that the EM bearing stiffness of 0.5~1.0E+6 N/m and damping of 2000 Ns/m are favorable for smooth operation of the system around the 2nd critical speed.

• Nuclear Engineering and Technology
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• 제40권4호
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• pp.299-304
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• 2008

A detection system was set up to measure the neutron generation rate of a recently developed D-D neutron generator. The system is composed of a Si detector, He-3 detector, and electronics for pulse height analysis. The neutron generation rate was measured by counting protons using the Si detector, and the data was crosschecked by counting neutrons with the He-3 detector. The efficiencies of the Si and He-3 detectors were calibrated independently by using a standard alpha particle source $^{241}Am$ and a bare isotopic neutron source $^{252}Cf$, respectively. The effect of the cross-sectional difference between the D(d,p)T and $D(d,n)^3He$ reactions was evaluated for the case of a thick target. The neutron generation rate was theoretically corrected for the anisotropic emission of protons and neutrons in the D-D reactions. The attenuations of neutron on the path to the He-3 detector by the target assembly and vacuum flange of the neutron generator were considered by the Monte Carlo method using the MCNP 4C2 code. As a result, the neutron generation rate based on the Si detector measurement was determined with a relative uncertainty of ${\pm}5%$, and the two rates measured by both detectors corroborated within 20%.

• 대한전기학회논문지
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• 제39권2호
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• pp.142-148
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• 1990

This paper deals with the desing method of Superconducting AC Generator (SCG). The establishment of design principle and design procedure of SCG are included in this study. Electric characteristics of SCG, such as synchronous reactance and sub-sub-transient reactance, are specified first as constraints and the size of SCG is calculated. Synchronous reactance and sub-sub-transient reactance are important factors because they determine the steady state and transient characteristics of SCG, respectively. A 20KVA SCG with double-shielded single-rotor is chosen for the case study. The design procedure proposed in this papar will also be applicable to large scale generators.